But what does it take to make money from these fast-growing industries, and which companies are leading the way? Welcome to our second annual paidContent 50 list — our attempt to answer those questions.

The paidContent 50 ranks digital-media companies based not on whether we like their products or are on a first-name basis with their CEOs. We use a very simple and objective metric: the revenue they earn from digital content, or from the adverting around that content. After all, companies ultimately need to earn revenue to survive and thrive — the more of it, the better.

Last year’s paidContent 50 focused on U.S. companies. This year, we’ve gone global, in an effort to better reflect changes in the industry itself. A growing number of content companies — Netflix, Sina and Spotify, among them — are aggressively pushing into overseas markets ater dominating at home. As that becomes a bigger focus for these companies, you can’t gauge their success without factoring in their track record internationally.

Creating this list wasn’t easy. We wanted digital revenue from the last full year, either calendar or fiscal, depending on the company. To get those numbers, we combed through public filings, read an ungodly number of news stories, and worked our network of contacts and analysts for data and background. Some media companies break out digital sales for everyone to see, but other companies (and not just startups) make it extremely difficult to discern. With some of those companies, our digital sales numbers are educated estimates based on our research, and in those cases, we list our sources and explain our math. (Read more about our methodology here.)

That Google tops our paidContent 50 list again this year may not come as a shocker. But there are definitely some surprises in this year’s crop of most-successful companies. How much do you know about South African publisher Naspers? Well, it dwarfs many U.S. household media brands when it comes to digital revenue. Twitter is hugely important media company, but it didn’t crack our list (and neither did The New York Times, for that matter). Amazon, on the other hand, is going gangbusters with content sales, as our writeup shows. And as with so many industries, China is becoming a power in media, too.

We’ve tried to be as scientific as possible with this list — the numbers are rooted in raw numbers, not emotions. But no such list is ever perfect. This is a work-in-progress; it’s aimed at starting the conversation about digital success. Please give us your feedback so we can make next year’s list even better.